This invention relates to an actuator device for a disc brake, primarily for a motor vehicle, the device including a rotary actuator operable, via a force transmission device, to move a friction element of the brake, in use, into engagement with a rotary brake disc. The invention also embraces a disc brake incorporating such an actuator device.
Our earlier specification W097/01045 discloses an arrangement in which a thrust member, through which force is transmitted from the actuator to the force transmission device, is held against rotation by engagement with a plate extending between the thrust member and a further such member carried by an adjacent force transmission device associated with the actuator. This arrangement is satisfactory in very large brakes, but cannot easily be accommodated in smaller brakes in which there may be insufficient space in the region of the force transmission device for the convenient incorporation of the aforementioned anti-rotational arrangement.
According to the present invention, an actuator device for a disc brake comprises a rotary actuator operable, via a force transmission device, to move a friction element of the brake, in use, into engagement with a rotary brake disc, and a thrust member arranged to transmit force from the actuator to the force transmission device, the actuator being arranged to engage the thrust member in a manner such as to prevent rotation of the latter.
Conveniently, the thrust member is received within a recess of the actuator and a defining wall of the recess engages the thrust member to prevent rotation thereof.
Typically, the force transmission device includes a pair of threadedly interengaged elements forming part of an extensible adjuster strut, one of the elements being held against rotation by a non-circular formation carried by the thrust member, conveniently in the form of an elongate stem extending into a complementary bore of the element.
From another aspect of the invention, there is provided a disc brake incorporating the aforesaid actuator device.
The invention will now be described, by way of example, with reference to the accompanying drawings in which: